On a shallow plate, combine the cornstarch, flour and salt.
Whisk eggs in bowl.
Dip chicken pieces in egg mixture and then flour mixture. Set them on a paper towel while the oil heats.
Heat 2 inches of oil in a heavy-bottomed pan until it reaches 375°F.
Add as many chicken pieces to the pan as can fit without being crowded. Cook for 2 minutes per side, until golden, then transfer to a wire rack. Continue with any additional chicken, until all is cooked.
In a medium pot, combine orange juice, brown sugar, soy sauce, vinegar, garlic, ginger, and red chili flakes. Bring to a boil. Mix together 1 tablespoon of cornstarch with 1 tablespoons of water. Add it to the boiling sauce and whisk until thickened. Add half of the orange zest.
Toss chicken with orange sauce. Garnish with green onion and remaining orange zest. Serve over rice, if desired.